想请问各位大大,为何图出不来
想了半天还想不出来><
希望各位大大能帮个忙帮我解惑...谢谢><"
U = UnitStep;
sol = DSolve[
{x''[t] + 3 x'[t] + 900 x[t] ==
100 t (U[t] - U[t - 1]) + 50 (U[t - 1] - U[t - 2]) +
100 (3 - t) (U[t - 2] - U[t - 3]), x[0] == 0, x'[0] == 0}, x[t],
t]
Plot[sol, {t, 0, 10}]